Torrential rains killed at least 17 people in the Somali capital overnight, bringing the death toll to 27 as a result of floods across the shattered African nation in the past week, officials and witnesses said on Sunday.

They said the victims, mainly children and the elderly, died after their mud-walled houses collapsed under heavy rain that pummelled several Mogadishu districts late on Saturday, leaving hundreds homeless and destroying property of unknown value.

Medics said relatives recovered more bodies from the drenched debris after the overnight downpour.

"The death toll has now reached 17. Some people have been recovered from houses that collapsed last night," said Abdullahi Sheikh Ali, nurse in the capital's Arafat hospital.

A pharmacist who treated injured victims said that a woman and one child were killed in the city's northern Suuq-Bacad district while five children were found dead inside a collapsed house in a nearby neighbourhood.

"It was a tragedy," said pharmacist Omar Mohamed Ali. "I treated four family members but the mother and a three-year-old child had died by the time I arrived at the scene."

"The rain was so heavy and their house was old and collapsed," he added.

The bodies of five children were recovered from another house in Wardhigley district south of Mogadishu.

Abdulahi Shirwa Nur, a relative of the dead children, told reporters the walls of the house had caved in.

A neighbour, Amino Abduweli Rage, said: "It was about 8.30pm when I was awoken by people shouting 'help'. I rushed to the scene and found people digging a collapsed part of a house and they recovered bodies of five children."

Three of the casualties were among the elderly living in a displaced people's camp in northern Mogadishu.

"In this camp, three people were drowned. All of them were elder people," said Sheikh Nur Hilowle, the chairman of the camp. Mogadishu is home to at least 250 000 people displaced by the conflict that has raged across the Horn of Africa nation for the past 15 years.

Residents said that at least 61 houses were destroyed by the heavy seven-hour downpour.

In August, thousands of Mogadishu residents were forced to flee to higher ground by flooding which destroyed dozens of makeshift homes.

Last week, heavy rains also killed at least 10 people in the country's southern Gedo region, which was recently hit by a scorching drought that put millions on people on the verge of starvation.

The latest deaths came amid heightened tension between increasingly powerful Somali Islamists and the fragile government over territorial control. Several bouts of fighting has forced thousands to flee into neighbouring Kenya from the southern region.

Humanitarian workers fear that the health of the displaced civilians would be affected since host aid agencies, including the United Nations, have pulled out of the country owing to deteriorating security.

Somalia, a nation of about 10-million, has lacked any disaster response mechanism since the country plunged into bloodletting after the 1991 ousting of dictator Mohamed Siad Barre.